Carburetor process for making n-vinyl compounds



Q Patented June 7, 1949 CARBURETOR PROCESS FOR MAKING N -VINYL COMPOUNDS Hans Beller, Craniord, and Robert E. Christ and Fritz Wuerth, Elizabeth. N. J., assignors to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application October 10, 1945,

Serial No. 621,621

4 Claims. (Cl. 260-315) The present invention relates to a process for producing N-vinyl compounds.

A process for producing N-vinyl compounds containing the pyrrole ring by reacting acetylene at elevated temperatures and preferably elevated pressures with compounds containing the pyrrole ring, for instance pyrrole, indole, carbazole, tetrahy-dro-carbazole, and naphtho carbazole in the presence of substances having a strongly alkaline reaction such as the alkali metals, their hydroxides and alcoholates has been described in United States Patent No. 2,066,160 to Reppe et al. A similar process for producing valuable N-vinyl compounds by reacting acetylene at elevated temperatures and preferably elevated pressures in the presence of alkali metals or alkali metal compounds having a strongly alkaline reaction with secondary N-diarylamines which are free from hydroxy groups has been disclosed in United States Patent No. 2,087,079 to Wolff. As secondary N-diarylamines there may be mentioned diphenyl-para-tolylamine a.,6'-dinaphthylamine, phenyl-a-naphthylamine, para-tolyl-e-naphthylamine and N-phenyl-Z-amino anthracene.

The use of elevated temperatures and preferably elevated pressures is necessary in order for the foregoing reactions to proceed satisfactorily. The inherent instability of acetylene at the preferred reaction conditions has seriously interfered with the use of this process. In order to render the acetylene reasonably safe, it has been necessary to dilute it sufllciently with inert gases, such as nitrogen, methane or hydrogen, in order to preclude explosions, a mixture of 2 parts of acetylene to 1 part of nitrogen by volume having been recommended. This dilution of the acetylene with inert gaseousdiluents has resulted in a substantial increase in the over-all pressure which is required and has materially lowered the rate of reaction and yield at any given reaction conditions. In addition to these and undesirable process effects, it has substantially increased the size of the plant and auxiliary equipment required in carrying out the reaction. We have now found that this reaction may be carried out at relatively lower pressures and with a relatively higher rate of reaction and yield under any given reaction'conditions if the acetylene employed in the process is mixed with a sufficient amount of the vapors of a volatile, normally liquid, organic diluent to eliminate the danger of explosion in the manner described in our copending application, Serial No. 621,620. When the acetylene is diluted in this manner with the vapors of a volatile, normally liquid, organic diluent, not only are the desired process effects of elimination of the dangers of explosion and, at any given reaction conditions, the improvement in yield and rate of reaction obtained, but in addition, the capital cost of the plant necessary for practicing th process may be substantially reduced.

In practicing the present invention, the acetylene is saturated or carbureted with the vapors of a volatile, normally liquid, organic diluent in any desired manner. It is preferable to introduce into the acetylene the required amount of vapors of a volatile, normally liquid, organic diluent while the acetylene is at a relatively low acetylene does not, perse, form a part of the present invention and numerous means for efiecting it have been described in our above-mentioned copending application, advantageously, the acetylene may be contacted with the desired diluent while the diluent is in liquid phase and is maintained at such a temperature that the acetylene will take up or become carbureted with a suflicient amount of vapors of the diluent that it will be non-explosive at the reaction conditions to be employed. In practicing the present invention, it should be borne in mind that in order to preclude the possibility of explosion, not only should the acetylene which is supplied to the reaction be diluted with the vapors of a volatile, normally liquid, organic diluent but any unreacted acetylene removed from the reaction mixture should be similarly diluted solong as it is-at an elevated pressure and/or temperature.

In practicing the present invention, acetylene at the predetermined pressure and temperature for the reaction and diluted with a suflicient amount of the vapors of an inert, normally liquid, organic diluent to eliminate the danger of explosion at these conditions is admixed with a compound containing the pyrrole ring or a secondary diaryl amine in the presence of a substance having a strongly alkaline reaction. The reaction proceeds most readily at a temperature of 200 C.

The diluent employed to carburize the acetylene may be any normally liquid organic compound having a relatively higher vapor pressure which is inert under the conditions of the reaction. As suitable compounds for use as such diluent may be mentioned the lower boiling liquid hydrocarbons, for example aliphatic or cycloaliphatic hydrocarbons such as hexane, heptane, octane, cyclooctane and others and isomers or mixtures thereof, also many aromatic or naphthenic hydrocarbons such as benzene, toluene, xylene and the like. In addition, certain heterocyclic compounds such as furfural, pyridine and the like are suitable for use and also such ethers as diethyl ether, unsaturated vinyl etherssuch as n-butyl vinyl ether, acetals such as dimethyl acetal and esters such as ethyl acetate, vinyl acetate and the like. The particular amount of inert diluent which should be employed will of necessity vary with the pressure at which the acetylene is with the particular diluent being used. The limits of explosibility or the degree of dilution which is necessary may be readily determined for any particular conditions by a simple preliminary test, for instance, by enclosing acetylene gas together with a predetermined amount of diluent vapor in a pressure vessel, heating the vessel to the test temperature and initiating a possible explosion by means of an electrically heated wire provided inside the pressure vessel.

The reaction may be carried out in the presence of inert diluents such as cyclohexane, benzene, toluene, tetrahydronaphthalene, decahydronaphthalene, and the like, which may be the same as or different from the diluent employed for the acetylene. Solid compounds such as carbazole are preferably made into a paste with a diluent of this kind and the necessary amount of strongly reacting substances to serve as a catalyst incorporated in the paste or suspension. The acetylene diluted to the necessary degree may then be admitted into the paste and the reaction mixture maintained at an elevated temperature, preferably between 100-200" C.

The vinyl compounds obtained by the process may be separated from the alkaline substances and purified by distillation if desired under reduced pressure, by extraction with suitable solvents or by crystallization. The preferred method of purification for any specific compound which is produced may readily be determined by one skilled in the art.

The following examples will further illustrate how the present invention may be carried out in practice but the invention is not restricted to these examples. The parts are by weight unless otherwise stated.

Example 1. A closed reaction vessel was charged with a suspension of 130 parts of carbazole in 212 parts of cyclohexane and a small amount of zinc oxide and sodium hydroxide. The system was then purged free of oxygen by means of nitrogen and the nitrogen then removed by evacuation. Acetylene at a pressure of four pounds per square inch was bubbled through a pool of cyclohexane maintained at 79 C. so as to saturate it with cyclohexane and the saturated acetylene then compressed to 170 pounds per square inch. The compressed saturated acetylene was heated to 145 C. and then introduced into the suspension of carbazole and catalyst in cyclohexane in the reaction vessel. During the reaction, unreacted acetylene was withdrawn from the reaction vessel and recirculated. When the theoretical amount of acetylene had reacted with the carbazole, in approximately 2 hours, the reaction mixture was allowed to cool. After cooling, it was filtered to remove insoluble catalyst and the filtrate subjected to fractional distillation, the vinyl carbazole being distilled under vacuum after removal of the cyclohexane. The yield obtained was 95 to 99 per cent of the theoretical yield.

In comparison with the above process in which a normally liquid inert diluent is employed for the reaction to carburize the acetylene, when a 60-40 acetylene-nitrogen mixture is employed in an otherwise identical process, the reaction requires somewhat higher pressures, a longer gxne (approximately 14 hours) and the yield is loser, amounting to only 90 per cent.

Example 2.A closed reaction vessel was charged with 300 parts of phenyl a-naphthylamine, parts pyridine and 9 parts of potassium hydroxide. The oxygen in the reaction vessel was then removed by means of nitrogen and the nitrogen recovered by-evacuation, and the mixture then brought to 160 C. Acetylene at a pressure of 4 pounds per square inch was bubbled through a bath of pyridine maintained at 114 C., where it became saturated with the pyridine and the saturated acetylene then compressed to 120 pounds per square inch. It was then heated to 145 C. and bubbled through the mixture in the proportions of 2 to 1 is employed in place of the acetylene carburized pyridine, temperatures of 180-l90 C. and pressures of 225-375 pounds per square inch are required.

We claim:

1. In the process of producing N-vinyl compounds wherein acetylene is introduced into a reaction zone and reacted therein, in the presence of a small amount of a compound having a strongly alkaline reaction, with an organic nitrogenous compound having a reactive hydrogen on the nitrogen thereof and selected from the group consisting of pyrrole compounds and secondary N-diarylamines known to be reactable with acetylene maintained in said reaction zone, said reaction being efi'ected at a predetermined temperature of from -200 C. and a superatmospheric pressure at which the acetylene ls normally explosive; the method of eliminating the danger of acetylene explosion and increasing the efilciency of the reaction which comprises contacting the acetylene which is introduced into said reaction zone while it is under non-explosive conditions of temperature and pressure with a volatile normally liquid inert organic compound which is non-explosive at said reaction conditions, said volatile normally liquid organic compound with which the acetylene is contacted being in liquid phase and being maintained at such a predetermined temperature that the acetylene becomes saturated with the vapors of said normally liquid organic compound in such an 5. amount as to form a mixture of acetylene and such vapors in such a predetermined ratio that said mixture is non-explosive at said normally explosive reaction conditions, adjusting the pressure and temperature of the thus-formed mixture to these normally explosive reaction conditions, introducing the thus-obtained mixture into said reaction zone while maintaining it at a temperature above that at which said vapors will condense and therein efiect the desired reaction between the acetylene and said organic nitrogenous compound and recovering the thus-obtained N-vinyl compound.

2. The Process as defined in claim 1, wherein the reaction between the acetylene and the organic nitrogenous compound eilected in the reaction zone as specified is carried out in the presence of an inert volatile organic diluent in liquid phase and in which said volatile inert organic diluent is employed as the volatile normally liquid inert organic compound with which the acetylene is contacted in the contacting step specified.

3. The process as defined in claim 1, wherein HANS BELLER, ROBERT E. CHRIST. FRITZ WUERTH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 662,258 Dickerson Nov. 20, 1900 928,867 James et al. July 20, 1909 2,066,160 Reppe et al. Dec. 29, 1936 2,123,734 Keyssner et al. July 12, 1938 

